20515021421 has 2 divisors, whose sum is σ = 20515021422. Its totient is φ = 20515021420.

The previous prime is 20515021381. The next prime is 20515021453. The reversal of 20515021421 is 12412051502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14910852100 + 5604169321 = 122110^2 + 74861^2 .

It is a cyclic number.

It is not a de Polignac number, because 20515021421 - 2⁶ = 20515021357 is a prime.

It is a super-2 number, since 2×20515021421² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20515024421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10257510710 + 10257510711.

It is an arithmetic number, because the mean of its divisors is an integer number (10257510711).

Almost surely, 2^20515021421 is an apocalyptic number.

It is an amenable number.

20515021421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20515021421 is an equidigital number, since it uses as much as digits as its factorization.

20515021421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 800, while the sum is 23.

Adding to 20515021421 its reverse (12412051502), we get a palindrome (32927072923).

The spelling of 20515021421 in words is "twenty billion, five hundred fifteen million, twenty-one thousand, four hundred twenty-one".